A, Cord-to-maternal transfer ratio, calculated as (optical density [OD]450-570 cord)/(OD450-570 maternal) for antibodies against influenza hemagglutinin A (HA), and SARS-CoV-2 receptor binding domain (RBD) and nucleocapsid (N). Significance was assessed with a 1-way analysis of variance followed by Tukey post hoc testing to determine the source of significant differences in antibody transfer ratios among HA, RBD, and N. Ig indicates immunoglobin; black lines, means. B, Correlation between cord-to-maternal antibody transfer ratios for the indicated antibodies. Significance and ρ were determined by Spearman’s rank correlation.
aP < .001.